The present invention relates to a circuit configuration for an automotive vehicle with traction slip control and in which traction slip control signals, including braking-pressure control signals and/or drive motor control signals, are derivable from sensor signals which represent the rotational behavior of the driven and the non-driven wheels.
In such control circuits, the information required for controlling the braking pressure and/or the vehicle drive motor are derived exclusively or predominantly from the rotational behavior of the individual vehicle wheels. Wheel sensors are available for this purpose, the output signals of which are evaluated and logically combined in an electronic circuit configuration. To accomplish an optimal traction slip control, a circuit configuration is required which reacts as sensitively and rapidly as possible to variations in the wheel rotational behavior being indicative of an unstable condition or an excessive amount of traction slip. However, to eliminate inevitable errors and tolerances, for example, in the measurement system and in the signal-processing system, the control must not respond until predetermined threshold values are exceeded. Additionally, uneven road conditions, bumpers, road holes and the like, cause variations in the wheel rotational behavior, chassis vibrations or axle vibrations which can initiate undesirable control actions and which cannot be eliminated by filter circuits or by augmenting the response threshold values without adverse effects on the control quality.
A method and a circuit configuration for suppressing undesirable control actions in anti-lock brake systems, which can be caused e.g. by chassis vibrations or axle vibrations, wherein a threshold value decisive for the initiation of the control is varied. The re-acceleration of the controlled wheel is known from German published patent application 33 45 729 (corresponding to U.S. Pat. No. 4,701,855). A wheel deceleration subsequent to re-acceleration of the same wheel is interpreted as an indication of a roadway obstruction, and a brake slip control action is prevented from being initiated due to this deceleration period.
An object of the instant invention is to improve the control quality of a circuit configuration for an automotive vehicle with traction slip control. Without curtailing the sensitivity of the control circuitry and the time of response to wheel lock tendencies, it is also an object to avoid that control actions are triggered by roadway obstructions.